1. Field of the Invention
The present invention relates to a connector system for a flexible circuit, and, in particular, to a zero insertion force connector system for interconnecting a flexible circuit to a substrate.
2. Description of the Prior Art
In general, mechanical connector structures in the form of an insulated housing with individual spring contact beams cannot be effectively utilized when the desired spacing between the conductors to which interconnection is desired is less than 0.050 inches. For such circumstances it is believed necessary to utilize a flexible circuit arrangement.
A flexible circuit is an electrical conductor structure in which a base sheet of polyimide or polyester film material has conductive tracings photolithographed thereon. Suitable for use as the base sheet for such flexible circuit arrangement is the polyimide or polyester film material such as manufactured and sold by E. I. du Pont de Nemours & Co. under the trademarks "Kapton" or "Mylar", respectively.
Such a flexible circuit may be interconnected with either a conventional circuit board substrate or another flexible circuit using any one of a variety of known connector constructions. For example, the flexible circuit may be wrapped about a core and the core secured in proximity to a substrate in the manner disclosed and claimed in U.S. Pat. No. 4,552,420 (Eigenbrode), assigned to the assignee of the present invention.
In another implementation the member to which the flexible circuit is to be connected may be clamped between a pair of parallel beams. This arrangement is shown in U.S. Pat. No. 4,647,125 (Landi et al.) and in the connector disclosed in U.S. Pat. No. 4,690,472 (Elco et al.), assigned to the assignee of the present invention. This last-mentioned patent is also noteworthy for its disclosure of wedge-shaped positioning guides which align the conductive features of the circuits being interconnected.
As another alternative the end of the flexible circuit may be bent around a mantle or curved tongue and brought into sliding engagement with the member to which it is to be connected. Contact with the flexible circuit is made by spring members. The flexible circuit trails rearwardly from the connector. This arrangement is believed exemplified in the connectors disclosed in U.S. Pat. Nos. 3,897,130 (Donnelley), 3,941,448 (Evans), 4,248,491 (Mouissie, also assigned to the assignee of the present invention), 4,684,183 (Kinoshita et al.) or 4,714,436 (Jones).
Still another form of flexible circuit connector utilizes a spring loaded clip arrangement in which the clips are opened to accept the end of the flexible circuit. When released the spring clips clamp the flexible circuit to the member to which it is to be interconnected. Representative of such connectors are those disclosed in U.S. Pat. Nos. 4,111,510 (Zurcher) or 4,252,389 (Olsson).
Yet another flexible circuit connector utilizes generally C-shaped spring clips in which the flexible circuit is brought to the connector from the closed end of the C-shaped clip. The flexible circuit is looped around the arms of the clip and the ends of the flexible circuit enters between the open ends thereof. The connectors disclosed in U.S. Pat. Nos. 3,614,707 (Zurcher), 4,416,497 (Brandsness et al.), 4,621,882 (Krumme), or Japanese Patent 3,069,171 (Fujitsu) are believed representative of this form of connector. Such an arrangement may be disadvantageous inasmuch as the looping of the flexible circuit may engender stress in the conductive tracings thereon, leading to premature cracking of the material of the tracings.